Custom Properties value in Animation Nodes
You can use expression node to control property of object. Use ctrl+shift+alt+c on a property to get code. use that code inside expression node to get or set the data.

For example an object Empty has two custom properties A and B. We can get value of A
using bpy.data.objects["Empty"]["A"]. Similarly we can set value to B using bpy.data.objects["Empty"]["B"]=x where x is the data we provide.



Or you can replace the object name and property name by,